AN8022L 查看數據表（PDF） - Panasonic Corporation
零件编号
产品描述 (功能)
生产厂家
AN8022L Datasheet PDF : 16 Pages
| |||
AN8022L, AN8022SB
Voltage Regulators
s Application Notes (continued)
[3] Design reference data
1. Setting the output frequency
The output is controlling the triangular oscillation with PWM control: Triangular oscillation frequency =
Output frequency
CT (C6) = Capacitor terminal for triangular oscillation
RT (C7) = Resistor terminal for triangular oscillation
VOSC − H−
VOSC − L−
[Reference calculation formula]
T1 = T2 =
C6 · V
2IRT (charge/discharge current)
V
Since the IRT is given by rough calculation of 2.5 V/RT and
V becomes approximately 3 V, the output frequency is obtained
in the following equation:
T1
T2
fOUT =
1
T1 + T2 =
IRT
C6 · V
=
5
6 · C6 · R7
However, it may deviate a little from the design value due to delay of the internal circuit.
(Reference value)
fOUT = approximately 200 kHz
at CT (C6) = 220 pF and RT (R7) = 19 kΩ
2. Setting the timer latch period
The timer latch period t, the period from the time when an abnormality of the power supply output is detected
to the time when the overvoltage protector is activated, can be set to any desired value by using the external
capacitance CTIM (C2) based on the following equation:
TIM/OVP = Capacitor terminal for timer latch period setting
[Reference calculated value]
t = C2 · VTIM [s]
ITIM
VTIM = 6 V (typ.): Over voltage protection threshold value
ITIM = Timer latch charge current
(Varies depending on R7 value, at R7 = 19 kΩ)
ITIM = 30 µA (typ.)
3. Setting the soft start time
• Soft start charge current
Most of the conventional ICs are charged by using the internal resistor from the internal reference voltage, or
by using the constant current source which is determined by the internal resistance. However, the above charging
method suffers from problems on dispersion or temperature change and can not ensure the soft start time. For this
reason, the AN8022L and AN8022SB use the following method: The soft start charge current is given from the
constant current source used in the internal triangular wave oscillation circuit. In addition, the above constant
current source is stable with respect to dispersion or fluctuation with temperature because it has the current value
which is determined by the external resistor and the terminal voltage given from the resistor-divider of internal
reference voltage. However, for this method, particular care should be taken on the application: Since each time
the setting of oscillation frequency is changed, the soft start constant should be also changed.
SS (C5) = Capacitor terminal for soft start
[Reference calculation formula]
t = C5 · VSS [s]
ISS
ISS = Soft start charging current
(Varies depending on R7 value, at R7 = 19 kΩ)
ISS = 30 µA (typ.)
VSS = 2.0 V, at duty = 0%
VSS = 4.1 V, at maximum duty
14
Share Link: 